Currently, there are many kinds of computer mouse available on the market, which are the most popular human-machine interface used by computers as cursor-control device. There are three basic types of mice, which are mechanical mouse, LED optical mouse and laser mouse with respect to the different means of detection. A typical mechanical mouse comprises a chassis containing a ball, with a part of the ball protruding through the underside of the chassis. When an user moves the mouse about on a flat surface, the ball rotates which is detected by the sensors arranged in the chassis. Unfortunately the moving parts of such a mouse can become dirty, causing the sensors to incorrectly measure ball rotation. A typical LED optical mouse has a small, red light-emitting diode (LED) that bounces light off that surface with sufficient roughness onto a complimentary metal-oxide semiconductor (CMOS) sensor. The CMOS sensor sends each image to a digital signal processor (DSP) for analysis, that the DSP is able to detect patterns of shadows generated by the roughness of the surface in the images and see how those patterns have moved since the previous image. Based on the change in patterns over a sequence of images, the DSP determines how far the mouse has moved and sends the corresponding coordinates to the computer. However, if the working surface of the LED optical mouse is a smooth surface made of marble, tile, or metal, etc., such mouse might not be able to operate without a hitch. A laser mouse is an advanced optical mouse, which is capable of emitting a coherent light so as to detect more surface pattern variation than the standard LED based optical mice. Nevertheless, such laser mice are not able to operate fluently while working on a transparent surface made of glass, acrylic, and so on.
In 1995, an input device is disclosed in U.S. Pat. No. 5,898,421, entitled “Gyroscopic Pointer and Method”, by Gyration Inc., which is a hand-held input device having an inertial gyroscopic element arranged therein, capable of being used either in free space, employing the inertial gyroscopic element for detecting angular velocity of a user's hand and thus defining movements of a cursor displayed on a screen of an interactive computer, or while sitting on a surface, employing either an optical element or moving part for detecting movement of a user's hand. An inertial mouse generated by the Gyration Inc. with respect to the referring patent is already available on the market, which is acting as a common LED optical mouse while it is sitting on a surface, and is acting as an inertial mouse using the inertial gyroscopic element to detect the angular velocity of rotation while it is operating in free space. Since the aforesaid mouse can be considered as a standard LED optical mouse with addition gyroscope arranged therein, it is conceivable that the cost of the referring mouse is comparably higher. Moreover, the pricey gyroscope further restricts the popularity of the inertial mouse, that is, the average price of a high-end mouse currently available on the market is about US$ 40.00 while a one-axis gyroscope will already cost about US$30.00. By virtue of this, the price of the “Gyration In-Air Wireless Optical Mouse” produced by the Gyration Inc. is about US$79.00, which is less competitive comparing to the optical mice, both in cost and in price.
In general, the drawbacks of this computer mouse with inertial gyroscopic element can be summing up as following:                (1) Since the aforesaid mouse is implementing optical sensors for detecting how far the mouse moved while operating on a flat surface, it will still has problems of power consumption and tracing capability similar to the typical optical mouse.        (2) Since the aforesaid mouse uses a gyroscope for detecting angular velocity of the mouse while operating in a free space, the use of the pricey gyroscope will cause the cost of the mouse to increase and thus the price of the mouse is too high to be competitive.        
Therefore, what is needed and would be useful is an inertial mouse capable of operating functional while sitting on a flat surface and in a free space, which is convenient to use and has high precision in movement detection.